1. Field of the Invention
The present invention relates to an external fixator for use in orthopedic surgical applications, and more particularly to a method and apparatus for external fixation of a hinged joint.
2. Discussion of the Related Art
In various orthopedic surgical procedures, it is necessary to secure two bone portions in a relatively fixed relationship to each other. For example, the need for establishing such a secured relationship is often a result of a fracture which has occurred to the bone. To ensure that the bone can regenerate in the proper orientation and fuse the fracture, it is important that the bone portions be fixed and in the desired position during bone regeneration.
Various external fixation devices for the repair of traumatized bone are known. For example, U.S. Pat. No. 5,662,650 to Bailey et al. discloses an apparatus for the external fixation of large bones. The apparatus is illustrated to include a main body as well as a first and second bone screw clamps. The main body serves to allow the apparatus to axially rotate, thereby providing a proper longitudinal rotational location of the bone screws with respect to a bone. The first bone screw clamp is used to secure a first bone screw to the apparatus while permitting the first bone screw to be axially displaced from the main body. In a similar fashion, the second bone screw clamp functions to secure a second bone screw to the apparatus and to allow the second bone screw to be axially displaced with respect to the main body. U.S. Pat. No. 5,662,650 is incorporated by reference as if fully set forth herein.
In certain orthopedic surgical procedures, it is necessary to employ an external fixation device for immobilizing or restricting motion of a hinged joint such as the elbow joint. Many known devices for externally fixating an elbow joint require the insertion of an axis pin through the anatomical pivot axis. Another known device for elbow fixation is disclosed in U.S. Pat. No 5,100,403 to Hotchkiss et al. which is entitled xe2x80x9cDynamic Elbow Support.xe2x80x9d The dynamic elbow support has proximal and distal support sections, means for rigidly connecting each support section to bone, and a pair of hinges connecting the support sections and pivoting at the joint. The pair of hinges permits movement of the support sections and their corresponding attached bone throughout flexion and extension. The hinge may be driven by a gear mechanism which may be disengaged by a clutch. The dynamic elbow support may also include a distraction mechanism for movement of the bones out of contact in the joint, while allowing for an active range of motion at the joint.
While known external fixators specifically designed for supporting a hinged joint may have proven to be acceptable for certain applications, such fixators and their application are nevertheless susceptible to improvements that may enhance their performance. In this regard, it is important that a mechanical pivot axis of an external fixator be aligned with the anatomical pivot axis of the hinged joint.
According to one aspect, the present invention generally relates to an apparatus for aligning a mechanical pivot axis of an external fixator with an anatomical pivot axis of a hinged joint. The hinged joint has first and second bones on opposite sides of the anatomical pivot axis. The external fixator has a central body connecting a first bone screw clamping assembly and a second bone screw clamping assembly. The central body includes the mechanical pivot axis. The apparatus for aligning includes an alignment member and a connecting member. The alignment member has a longitudinal axis for alignment with the anatomical pivot axis. The connecting member is adjustably secured to the alignment member and adjustably secured to the first bone screw clamping assembly.
According to another aspect, the present invention relates to a method of aligning a mechanical pivot axis of an external fixator with an anatomical pivot axis of a hinged joint. The hinged joint has first and second bones on opposite sides of the anatomical pivot axis. The method includes the steps of providing an external fixator having first and second bone screw clamping assemblies connected by a central body, the central body having a mechanical pivot axis. The method additionally includes the steps of securing the first bone screw clamp assembly to the first bone through at least one bone screw and aligning an longitudinal axis of an alignment member with the anatomical axis. The method further includes the steps of interconnecting the alignment member with the first bone screw clamp assembly and aligning the longitudinal axis of the alignment member with the mechanical pivot axis.
An advantage of the present invention is the provision of a method and apparatus for external elbow fixation which allows for optimal alignment through hinge positioning which is independent from bone pin placement.
A related advantage of the present invention is the provision of a method and apparatus for external fixation which affords flexible pin placement to avoid damage to local neurovascular structures and ligaments.
Another advantage of the present invention is the provision of a method and apparatus for external elbow fixation which permits movement of a hinge assembly relative to bone pins engaged with the humerus and ulna.
Another advantage of the present invention is the provision of a method and apparatus for external elbow fixation which allows complete radiographic access of the elbow joint from the lateral view to determine xe2x80x9cbest fitxe2x80x9d hinge axis.
Another advantage of the present invention is the provision of a method and apparatus for external elbow fixation which facilitates elbow joint distraction.
Another advantage of the present invention is the provision of a method and apparatus for external fixation of an elbow joint eliminates the requirement for an elbow axis pin.
Another advantage of the present invention is the provision of a method and apparatus for precise alignment of a mechanical pivot axis of an external fixator with the anatomical pivot axis of a hinged joint.
Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.